Authorities discovered the remains of a newborn baby behind a home at 384 Lake Ave. Monday after someone reported to police that an unusual odor was coming from a bag.

"At 8:43 a.m., police officers responded to the police station lobby for a report of someone wanting to report an unusual odor coming from a bag at 375 Lake Ave.," police said. "Upon arrival, they spoke to the complainant. He said that he observed a bag with an unusual odor and was worried about what was inside."

Officers went to Lake Avenue and found a garbage bag emitting a "strong odor" behind 384 Lake Ave., police said. Inside that bag was the remains of a dead baby.

Police saw a man and woman walking behind the address near private railroad tracks and a prominently posted "No Trespassing" sign. They were subsequently arrested.

Edwin Santiago, 31, of 384 Lake Ave., and Jennifer Rheaume, 36, of 375 Lake Ave., are being charged with removal of a human body and concealment of the death of a child, police said. They are also being charged with walking on railroad tracks.

Authorities learned a woman staying at 375 Lake Ave. was several months pregnant recently. The owner of 375 Lake Ave., Mark Healy, told MassLive that a pregnant woman named Jennifer was, in fact, staying at his home.

He did not know her last name and said she was recently released from a rehabilitation program.

Healy said he noticed within the past week that the woman was no longer pregnant.

A neighbor living not far from the scene told MassLive that she interacted with the same woman within the last few days and she was not pregnant.

"She never went to the hospital," Healy said. "But there was no baby."